There are devices in the prior art which break the fall of somebody operating at a height e.g. on the external wall of a building, in shipyards, in rescue situations or in mountaineering sports, where that person is fitted with a safety harness and lifeline.
The known devices comprise an opening element, which is substantially cylindrical when closed in use and through which the lifeline is free to run under normal working conditions.
A portion of the wall of the cylindrical element comprises a floating or swinging cam with a knurled or ribbed face which is in its turn linked by a suitable means to the user's harness. When a fall occurs, the weight of the person (who falls faster than the cylindrical element movement along the lifeline) acts on the cam and causes it to rotate so as to force the knurled face against the lifeline, slowing the run of the line through the cylindrical element and arresting the fall of the wearer.
Such devices present the following drawbacks: the weight of the user acts directly on the cam in such a way as to make it very difficult to unblock the run of the line, once the fall has been arrested and this prevents the person from descending unaided. The presence of knurling on the face of the cam could damage the lifeline, the instant the device starts to operate, due to friction between cam and line. Such devices do not have a means of reducing the time to break the fall and cannot guarantee optimum safety.